The capacitance video disc system described by Clemens in U.S. Pat. No. 3,842,194, requires a pick-up stylus adapted to track in a very small groove in a vinyl disc record coated with a conductive layer and having a dielectric layer disposed thereover. When relative motion is established between the disc record and the pick-up stylus, the pick-up stylus cooperates with the disc record to establish capacitance variations between the stylus and the record due to geometrical variations in said grooves. The stylus includes a support element with a conductive element disposed on one surface. The support element is shaped in a manner such that when it engages the record medium groove, an edge of the conductive element is adjacent to the dielectric coating. U.S. Pat. No. 3,826,877 to Leedom describes a stylus made by depositing tantalum on a sapphire support. In the manufacture of such styli, the sapphire support is abraded with diamond abrasive to form a grooved surface and tantalum metal is vacuum sputtered over the grooved surface to a thickness of about 1,000 to 2,000 angstroms. Chips are cut in the general size of the stylus. The chips must then be rough lapped to give the approximate shape of the stylus, and then fine lapped to conform the stylus tip to the shape of the groove. The metal film must adhere tightly to the sapphire substrate during these operations and further, the metal-to-substrate bond must survive many hundreds of hours of playing time during which the stylus surface is abraded by the revolving disc. If the metal film detaches from the very edge of the stylus, even for as little as 50 angstroms from the edge of the stylus in contact with the disc, a noticeable and unacceptable reduction in signal output occurs.
Thus it would be desirable to provide the best adhesion between conductive metal films and alumina substrates for this application.